Process for producing filaments and films of polymers of alkylene sulfides



W. J. PoLEsTAK 3,539,676 PROCESS FOR PRODUCING FILAMENTS AND FILMS OFNov. l0, 1970 POLYMERS 0F ALKYLENE sULFIDEs Filed Aug. 29, 1966/m/e/w-OQ hun? d. poLSmK ByC 6 United States Patent Or 3,539,676 PROCESSFOR PRODUCING FILAMENTS AND FILMS OF POLYMERS OF ALKYL- ENE SULFIDESWalter J. Polestak, Summit, NJ., assignor to Celanese Corporation, NewYork, NX., a corporation of Delaware Filed Aug. 29, 1966, Ser. No.575,722 Int. Cl. B28b `3/20; D01d 5/22; D01f 3/10 U.S. Cl. 264-176 10Claims ABSTRACT OF THE DISCLOSURE A process for producing hard stretchfilaments and films of alkylene sulfide polymers, such as polyethylenesulfide, having an inherent viscosity above 0.5, involves extruding theheat softened polymer through a shaping orifice to form the filament orfilm and taking up the product at a linear rate of from about 20 to3,000 meters per minute, preferably at a linear rate of from 1500 to2500 meters per minute at a drawdown ratio of from 100:1 to 4000:1. If afilament is formed and a drawdown ratio greater than 120011 is used, thefilament spontaneously develops helical crimps along its length.Opencelled filaments or films are produced from the hard stretchfilaments and films by stretching the filaments or films in a range offrom about 25 percent of the unstretched length up to about 90 percentof the breaking elongation, e.g., from 0.5 to times the unstretchedlength. To stabilize the open-celled structure, the stretched filamentor film may be heated while in the stretched state to a temperature inthe range of from about 80 C. to a temperature below the melting pointof the polymer.

This invention relates to a preparation of filaments and films frompolymers of alkylene sulfides, more particularly, this invention relatesto the melt spinning of filaments and films exhibiting hard stretchcharacteristics from polyethylene sulfide.

As used herein, the term hard stretch signifies those product propertiescharacterized by high elongations, low tenacities, relatively lowmodulus values, high tensile recoveries and significant yield stresses.

It has been proposed to prepare polymers of alkylene sulfides, e.g.polyethylene sulfide, into filaments and films by extrusion inheat-softened or molten form through suitably shaped orifices withcooling of the extruded material. The use of such polymers has, however,heretofore been restricted by difficulties encountered in successfullyconverting the polymers into the useful filaments and films.

According to the present invention, a heat-softened or molten polymer ofalkylene sulfide having an inherent viscosity of about 0.5 or greater isextruded through a shaping orifice to form a filament or film productwhich product is taken up on a bobbin or a roll at a linear rate of fromabout 20 meters per minute up to a rate of about 3000 or more meters perminute. Preferably, the product is taken up at a linear rateconsiderably more than the aforesaid lower limit, e.g. at a rate withinthe range of from about 1500 meters per minute up to about 2500 metersper minute. It has been found that at these high take-up speeds thefilaments or films obtained from the polymers of alkylene sulfideshaving relatively high inherent viscosities are of industrial utility.

As used herein, the term inherent viscosity is defined as:

wherein c is the concentration in grams of polymer in 100 ml. of theparticular employed solvent and (n),r is

ice

the relative viscosity which is the ratio of the flow times in aviscometer of polymer solution and of solvent at C.'The inherentviscosity is indicative of the molecular weight of the polymer.

The monomers from which the polymeric starting materials of the presentinvention are employed are alkylene sulfides which have the generalformula:

where R, R', YR and R may be, for example, hydrogen, an aliphaticradical, a cycloaliphatic radical, an aryl radical, etc. The Rs may alsobe joined to form a cyclic structure. In cases where one or more of theRs contain an epoxide group, a diepoxide or polyepoxide results, for thepurposes of simplicity, this disclosure will consider only the materialswith one epoxide group. This is not, however, to be considered as alimiting factor of the invention.

The alkylene sulfides will react under suitable conditions to built uppolymer chains of considerable length. If desired, they may be reactedwith other organic or inorganic molecules. Examples of material whichcan be made to react with the alkylene sulfides are well known in theart. The general formula for the resulting polymer of alkylene sulfide,exclusive of extraneous monomers, may be represented as follows:

R R eine where R, R', R and R" are as described above and n is number ofmonomer units in the chain. Thus, the polyalkylene sulfides suitable foruse herein will comprise a predominance of the foregoing recurringunits.

In accordance with the present invention, a relatively high molecularweight polyethylene sulfide having a high inherent viscosity i.e. aninherent viscosity of 0.5 and greater is a preferred fiber-formingmaterial. This material which is solid and crystalline having a meltingpoint of at least 200 C. and preferably between 208 and 212 C. may beprepared by polymerizing ethylene sulfide in a medium virtually devoidof elemental oxygen, and in the presence of a catalyst which is theproduct of the reaction of the zinc-diethyl on water. The properties ofa typical polyethylene sulfide material suitable for use in the presentinvention is given on the following Table I.

TABLE I.-POLYETHYLENE SULFIDE Flexural modulus Izod impact Tensileimpact Shear strength" 7,800 .s.i D-732. Taber abrasion 7.3 mg. at 1,000eycles D-1242. Hardness M-85 D-785. Water absorption 0.033% (24 hrs. at23 C.) D-570.

To carry out the process of the invention, a heatsoftened or moltenpolymer is extruded through an orifice having at least one smalldimension, e.g. of 0.05 to 5.0 mm. The process is particularly useful inthe case of the melt spinning of filaments, e.g. wherein the dimensionsof the orifice in all directions are within the foregoing range. In thecase of the extrusion of polyethylene sulfides, the temperature of thepolymer being extruded may be, for example, in the range of about to 300C. and preferably in the range of between 2201 and 270 C.

Of course, the above temperatures may be either raised or loweredaccording to heat stability of the polymer employed, as well as theconditions utilized, e.g. residence time, etc. While a minimum lineartake-up speed of more than meters per minute is used substantiallyhigher take-up speeds are preferably employed, e.g. take-up speeds of1500 to 2500 meters per minute or even higher, using a draw-down ratioin a range of, for example, 100 to 4000.

The drawdown ratio or spin dra-w ratio is the ratio of the velocity ofinitial fiber take-up to the linear velocity of the extrusion of themolten polymer.

Pilaments having deniers in the range of, for example, 1 to 15 are ofgreatest general interest but the invention may, if desired, be employedin making much heavier filaments of up to, for example, 100 denier aswell as in making films in a broad range of thicknesses. The pressureexerted on the polymer to effect extrusion is usually several hundredpounds per square inch, for instance it may be from 500 to 5000 p.s.i.or higher.

In general, the polymer may be extruded into the air at roomtemperature. However, it may, if desired, be extruded into an atmosphereof inert gas, e.g. nitrogen, argon, steam or carbon dioxide or into aliquid such as water, acetone or methylene chloride at a temperature lowenough to set the extruded material. The gas on the downstream side ofshaping orifice may be circulated for a better heat transfer.

One of the advantages issuing from the instant invention is that thefilaments and films obtained from the process are commercially usefulwithout applying a separate drawing operation, e.g. they may be suitablyemployed without being subjected to a cold or hot drawing step.Obviously, the deletion of this operation and the apparatus utilizedtherewith represents an advantage which inures to the commercial aspectsof the invention.

The properties of the shaped article resulting from the process of theinvention are especially attractive when there is incorporated in thepolymer a thermal stabilizer which may be an antioxidant, as for examplea phenolic compound, e.g. an alkylene bisphenol in which the alkylenegroup contains up to 4 carbon atoms and each phenolic ring issubstituted with up to four alkyl groups each of which contains up to 6carbon atoms. A typical example is 2,2methylene bis-(4-tertiarybutyl--methyl phenol) or a monocyclic alkyl phenol containing up to 4alkyl groups on the ring each of which contains up to 6 carbon at MS, anexample of which is di-tertiary butyl methyl phenol. Stabilizer may beused in an amount of from 0.01 to 5.0 percent based on the weight of thepolymer.

The filaments and films resulting from the aforesaid process areespecially advantageous as precursors for the preparation ofcorresponding articles having an opencelled structure with minute cells,e.g. cells smaller than those which can be measured by an opticalmicroscope and having apparent densities significantly lower than theapparent densities of the corresponding precursor, eg. filaments andfilms having no open-celled or other voidy structure.

As used herein, the term apparent density signifies the weight per unitof gross volume of the filament or film, where gross volume is theproduct of the measured length of the weighed filament or film and theaverage cross-sectional area of the fibers as calculated on the basis ofmeasurements made with an optical microscope.

As used herein, the term open-celled structure signifies that the majorportion of the void or pore space of the structure within the geometricconfines of the filament or film is accessible to the outside geometricsurfaces of said filament or film.

In accordance with this embodiment, the precursor material is subjectedto a stretching operation in order to form the voids in the low densityproduct, e.g., stretching the precursor material in a range of fromabout percent of the unstretched length of the precursor material up toabout 90 percent of the breaking elongation of the precursor material atthe stretching temperature. The stretching of said precursor may becarried out at any temperature below the melting point of theproduct-forming polymer. The stretching operation may be effected in aconventional manner. Thus, the stretching may be conducted by passingthe precursor material through a hot medium conventionally employed inthe art of stretching, such as hot air, hot water or pressured steam,preferably at a temperature between 90 C. and 140 C. During the passagethrough the hot medium a high stretching ratio is preferred, e.g.usually the precursor material is stretched from .5 to 10 times theiroriginal length. As mentioned, it is during this stretching stage thatthe opencelled structure, i.e. the voids present in the product isformed.

If desired, the thus-stretched product may be subjected to a heatsetting or annealing step while in a stretched state. This step isgenerally most effective at a temperature in the range of from about C.to a temperature below the melting point of the fiber, and preferablybetween about 100 C. and the melting point of the fiber. The period forheat setting should be longer than about 0.1 second and may be withinthe range of from about 0.5 second to about 30 minutes, preferably about2 seconds to 15 minutes. The stretching and heat setting operations maybe carried sequentially or they may be combined into a single operation,e.g. by stretching the low density article over a metal surface heatedto the required temperature.

The heat setting or annealing step referred to may be carried out, forexample, in an oven heated to the appropriate temperature.Alternatively, the heat setting may be applied in a continuous run ofthe film or bundle of filaments. Such heat treatment may `be by means ofhot fluid, eg. in a jacketed tube or shroud, lby infrared rays, bydielectric heating or vby direct contact of the running film or filamentibundle with a heated metal surface, preferably curved to make goodcontact. For heat setting fibers in the stretched state, such fibers maybe stretched on a conventional draw frame and rewound on a bobbin andsubjected to heat setting in that manner or the material may bestretched and heat set in a continuous fashion by means of two sets ofdriven rolls traveling at different speed with the filamentary materialbetween thc rolls passing through heated tube or over a heated metalsurface.

The filaments and films resulting from the stretching operation, in atensionless state, have apparent densities lower than the densities ofthe polymer materials from which they are formed, usually no greaterthan preferably about 50 to 75% of the densities of the correspondingpolymer materials. The sizes of the passageways to the void or porespaces of the open-called structure accessible to the outside of thefiber are under 5000 angstrom units, eg. 150 to 5000 angstrom units, asporosimetrically determinel by mercury penetration which measurementalso determines the volume of such void or pore space. While thefilaments and films thus obtained have void or pore spaces distributedthroughout the same, as mentioned, yet they have mechanical propertiescomparable with those of conventional polyalkylene sulfide filaments andfilms, i.e. products of conventional densities. Thus, for example, thefibers with such voids of this invention can have a strength of 1- g./denier and an elongation of 20- The final crystallinity of these lowdensity products is at least 30%, more preferably at least 40% and mostpreferably at least 60% e.g. 50-100%.

Since the filaments and films in this embodiment of the inventioncontain numberless voids, they satisfactorily absorb various dyestuffssuch as azoic or naphtho dyes, dispersed dyes, oil dyes, metallizeddyes, vat dyes, sulfur dyes, basic dyes, mordantable dyes, and the like,so that they are readily dyed deeply and uniformly. Furthermore,

the open-celled products can uniformly and sufficiently absorb othertreating agents such as polymerizable compounds, e.g. vinyl monomers,heat-stabilizers, light-stabilizers, antistatic agents, and the like.Various other treating agents such as surfactants, softeners, flameresistors, etc. are also satisfactorily absorbed by the novel 'fibers ofthis embodiment of the invention.

The filaments and films spun from polymers of alkylene sulfides inaccordance with the invention may be utilized for a variety of possibleapplications, for example, fibers or filaments having substantially lowapparent densities than those heretofore obtained would be extremelyuseful in products requiring a high degree of insulation from heat orcold, fiberll applications requiring a high degree of insulation, e.g.in sleeping bags and quilts, and as a general insulation material.Moreover, synthetic products of particularly low apparent density havethe economic advantage that they may be often used for the same purposesas products of conventional density but with the employment of a muchlower weight of material.

The unstretched or procursor fibers or filaments spun from polymers ofalkylene sulfiles may also be utilized in a variety of applications. Forexample, they may be drawn and used as continuous filament yarns or theymay be drawn and cut into short lengths and further processed as staplefiber in which form they may be processed on conventional textilemachinery, either alone or mixed with other natural or synthetic fibers.Staple fibers may be utilized for producing filling materials of highbulk. It is an essential part of the staple fiber process that a wavy orcrimped form should be imparted to the fibers to assist their processingon conventional textile machinery, especially when mixed with naturalfibers having this wavy or crimped form. The crimping of the fibers alsoimparts softnes and bulk to yarns produced from them, leading to greaterWarmth in fabrics produced from such yarns.

The process of crimping the fibers has heretofore been an additionalfalse-twisting step included after the drawing step in staple fiberproduction. Filaments spun from polymers of alkylene sulfides may alsobe utilized as textured or bulk filament yarns, but advantageously,without the requirement of the additibnal step, i.e. false-twistingstep, required by conventional methods.

Surprisingly, it has been found that by conducting the spinning processin such a way that the drawdown ratio is adjusted to a ratio of morethan 1200:l and, to between 1500:1 and 3000:l and that the fiber-formingpolymer has an inherent viscosity between about 0.5 and 1.5 and higher,that on relaxation of the spun yarn, it will spontaneously take up ahelical form.

Thus, in accordance with this embodiment of the present The followingexamples further illustrate the invention:

EXAMPLE I In these examples, a sample of polyethylene sulfide wasutilized having the characteristics set forth in Table II:

TABLE II Characteristics of polyethylene sulfide polymer CrystallineMelting Point, C.:

ln air 20.8 In air 202-205 In Dow Corning Silicone 550 Fluid 203-207Birefrigence on Cooling, C. 18S-180 Elemental Analysis, percent:Theoretical 6.6-H 6.6. Density, g./crn. at 25 C 1.28.

I.V. (98/ 2 p-chlorophenol/a-pinene at 120 C.) 0.97. KD23O 0.01.

Stabilizer-antioxidant A hindered phenol. Polymerization catalyst systemA prOduCt reaction of zinc-diethyl on water.

In order to prepare a polymer for melt spinning, a polymer sample whichoriginally was in tensile bar form, was pulverized and then thoroughlydried in a vacuum oven at 90 C. and at a pressure of 100 microns forseveral hours prior to rod formation. Despite appropriate coolingconditions an LV. loss was encountered in the pulverizing operation,i.e. pulverized powder LV. was 0.86. Rods were prepared by compression(4000 p.s.i.g.) at 100 C. followed by a 30 minute holding cycle at 150C.

The densied polymer was extruded on a micromelt constant pressureextruder activated by a hydraulic air cylinder.

Drawdown values were determined from the ratio of the spinneretteorifice area to the cross-sectional area of the monofilament as measuredlby its denier.

In the classification of spinnerettes, the L/D ratio refers to thelength and diameter of the capillary. The countersink angle for thespinnerettes utilized was Drawing results were obtained with a hot shoedraw frame.

Table III illustrates a series of runs employing the aforesaidtechnique. Table III further illustrates that polymer fiber propertiesimproved with increased take-up speeds (drawdown) at a given throughputrate.

TABLE IIL-SPINNING EVALUATION OF POLYETHYLENE SULFIDE [Pulverized SampleLV.: 0.86]

Spinnerei: dimensions Take-up Tensile property range Spinning speedFiber L/D, Diameter, temp., range, A Elong.. Tenacity, LV., ratio milsC. nL/min. Denier' percent g./d. range 230 1, 000-2y 200 l. 0-2. 370-l30 0. Sel. 3 0. 4-0. 5 230 0 4. 6 15 0. 7 0. 4 220 800-2, 200 0.0-1. 9 80-120 0. 7-l. 1 0. (i 220 30 50-60 6 0. 5 0. 5-0. (i 22010U-800 1. 3-4. 6 l00-230 0. 7-1. 2 0. 7 210 60G-800 l. 5-2. l 140-1700. 8e1. l 0.7 210 25-370 3. 1-20 0-50 0. (i 0. 6-0. 7 1 210 22 60 6 0. 50. 8

1 Initial extrusion preceded by a yi hour residence time at 210 C.

EXAMPLE II invention, a process is provided for the preparation ofpolyalkylene sulfide filaments or staple fibers cut therefrom, having ahelically crimped form and characterized in that the crimped form isspontaneously developed by spinning the filaments of polyalkylenesulfide at a high winding speed from a polymer which provides thenecessary inherent viscosity. Preferably, in this embodiment,

In this example a spinning run was effected with a polyethylene suldepolymer in order to illustrate the spinning instability (associated withpoor tensile property development) which can 4be primarily attributed tothe low inherent viscosity (rIlV.) values of the polymer and evidencesthe necessity of employing a polymer with melt temperatures of from 220to 270 C. are employed. 75 a high LV.

7 TABLE 1v MICRO-MELT SPINNING OF POLYETHYLENE SULFIDE POLYMERSSpinneret: L/ D: 1.3, 14 mils diameter EXAMPLE III This example comparespolyethylene sulde fiber tensile and elastic properties with some hardstretch fibers, viz. a hard stretch polypropylene and a hard stretchacetal polymer. Tables V and VI evidence the similarity in 'behaviour ofthe various polymers.

of increasing of the liber, the ratio of total gross volume of stretchedto unstretched material is often less than one, i.e. the apparentdensity of the stretched fiber is higher than that of the unstretchediber. Expressed another Way, the diameter of an elastic ber of rubber orspandex, or of an ordinary inelastic iiber which is stretched toincrease orientation, decreases on stretch to the extent that the lengthof the liber increases so that the total gross volume of the stretchedliber is approximately equal to or less than that of the unstretchedfiber. This is in contrast to what occurs when an elastic crystallinepolyethylene sulde fiber contemplated by this invention is stretched.The decrease in the diameter of such a fiber on stretch is either zeroor very small and such a decrease in diameter does not make up for thelength increase on stretch, so that the total gross volume of thestretched liber is substantially higher than that of the unstretchedfiber. As the total gross volume of the liber being stretched increases,its apparent density decreases proportionately.

Moreover, if the stretching tension on the relatively TABLE V.-TENSILEAND ELASTIO PROPERTIES [Comparison of Polyethylene Sulfide to HardStretch Fibers] (TEST TEMPERATURE AND CONDITIONS, 23 C., DRY) Elasticproperties Work recov- Permanent Tensile properties ery, percent set,percent extension extension Elong., Ten., Mod., Fiber Denier percentg./d. g./d. 5% 10% 5% 10% Pol eth lene sulfide:

yS y 1. 3 113 1. 2 16 90 62 7 13 1. 4 116 0. 9 17 73 50 11 14 4. 6 2160. 7 71 48 6 13 1. 5 136 1. 2 1S 66 52 7 13 7. 7 200 1. 5 25 50 46 4 54. 0 250 1. 3 25 45 31 (l 12 1 Average values. 2 Average values.

TABLE VI.-ELASTIC PROPERTIES [Comparison of Polyethylene Sulde to HardStretch Fibers (Strain Rate of 100%/niinute)] Modulus, g./d. WorkPermanent Fiber recovery, set, 050, 1st 2nd Fiber condition Denierpercent percent g./d. cycle cycle Polyethylene sulphide #1 As 23. 4 19.3 0. 88 18 6 27. 0 l. g 9(1i 20 8 Pol eth lene sul hide #2 A 20.6 2 .9 77 y y p 23.8 17. 6 0. 84 7 Hard stretch polypropylene 1 35-40 1-3 0.9-1. 4 Hard stretch acetal polymer 2 -do 17-25 7-15 0. 6-1. l

1 Range of elastic properties. 2 Range oi elastic properties.

EXAMPLE IV crystalline elastic iibers as described in the preceding Inthis example two polyethylene sulfide ber samples (corresponding to RunNos. 3a and 3b of Table III) were extended in the manner herei'ribeforedescribed and the resulting volume ratio was noted. The volume ratio isthe ratio of the fiber volume at a given extension to its volume at zeroextension. These were calculated from fiber diameters determinedmicroscopically at the different extension levels. The resulting data ispresented in graphical form in FIG. I which is incorporated herein byreference.

The graph of FIG. l illustrates the phenomena that if a polyethylenesulfide liber, spun in accordance with this invention is subjected to adegree of stretch below its breaking point, the ratio of the total grossvolume of the stretched liber to that of the unstretched fiber issignicant- 1y greater than one. This is very surprising and totallyunexpected since the ratio of total gross volume of a given mass of afiber of an elastic material such as rubber or spandex in the stretchedstate to that of the iiber in the unstretched state has been found to besubstantially one, i.e. there is no increase of total gross volume ofthese ibers when they are stretched. Moreover when a conventional fiber,e.g. of nylon, polyester or polypropylene, is inelastically stretched,i.e. cold drawn, for the purpose paragraph is released, the grossvolumes and apparent densities of the bers tend to revert backsubstantially to those of the bers in the unstretched state. That is tosay, the gross volume increase and apparent density decrease arereversible. However, it has ybeen found that, if these fibers are heattreated properly in the stretched state, they may be stabilized so as tomaintain their high gross volume and low apparent densitycharacteristics after the stretching tension is removed.

The values of tenacity, breaking elongation and modulus referred toabove are determined in a conventional manner with the use of an InstronTensile Tester operating at a strain rate of 60% /min. The initialmodulus, as the term is used above, is determined by measuring the slopeof the stress-strain curve at the point indicated by 1% strain.

The values of elastic recovery given above, unless otherwise noted, aredetermined with the Instron at a strain rate of 10% /minute After theyarn is extended to the desired strain value, the jaws of the Instronare reversed at the same speed until the distance between them is thesame as at the start of the test, i.e., the original gauge length. Thejaws are again reversed after two minutes and are stopped as soon as thestress begins to increase from 9 the zero point. The elastic recovery isthen calculated as follows:

above are crystalline melting points, i.e. temperatures at l which allcrystallites in a polymer disappear as indicated by loss ofbirefringence when the polymer is examined with a polarizing microscope.

The term porosimetrically determined by mercury penetration means thatthe open-celled nature of the structure and the approximate size of thepassageways to the surface of the pores or lvoids making up suchstructure are determined with a porosimeter as described in an articleby R. G. Quynn in the Textile Research Journal, vol. 33, pages 21 etseq. (1963).

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from the spirit of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are dened as follows:

1. A process for the production of filaments or lms from a polymer ofalkylene sulfide having an inherent viscosity greater than about 0.5which comprises extruding the heat-softened polymer through a shapingorice to form a iilament or lm and taking up the product at a linearrate of from about to about 3,000 meters per minute and at a dra-wndownratio in a range of from about 100:1 to 4000z1.

2. The process of claim 1 wherein said polymer is a polymer ofpolyethylene sulde.

3. The process of claim 1 wherein the product is taken up at a linearrate of from 1500 to 2500 meters per minute.

4. A process for the production of laments or lms having an open-celledstructure from a polymer of alkylene sulfide having an inherentviscosity greater than about 0.5 which comprises extruding theheat-softened polymer through a shaping orifice to form a filament orfilm, taking up the product at a linear rate of from about 20 to about3000 meters per minute, and stretching said product in a range of fromabout 25% of the unstretched length of the product up to about 90% ofthe breaking elongation of the product at the stretching temperature toproduce a stretched product having an opencelled structure and a reducedapparent density, the

open cells having entrance passageways no larger than about 5000angstroms as porosimetrically determined by mercury penetration.

5. The process of claim 4 wherein the polymer is polyethylene sulde andwherein the stretching is conducted at a temperature between C. and 140C. and the product is stretched from 0.5 to 10 times its unstretchedlength.

6. The process of claim 4 wherein said product is taken up at a linearrate of from about 1500i to about 2500 meters per minute and at adrawndown ratio in a range of from about :1 to 4000:1.

7. The process of claim 4 wherein said stretched product is heated Whilein the stretched state, to a temperature in the range of from about 80C. to a temperature below its melting point.

8. A process for the production of crimped filaments from a polymer ofalkylene sulde having an inherent viscosity greater than 0.5 whichcomprises spinning the heat-softened polymer through a spinnerette toform a lament, drawing said lament at a draw-ratio of more than 1200:1and releasing the drawing tension whereby said filament develops helicalcrimps.

9. The process of claim 8 wherein said draw-ratio is between about1500:1 and 300:1.

10. The process of claim 8 wherein said polymer is polyethylene suldehaving an inherent viscosity of from about 0.5 to about 1.5.

References Cited UNITED STATES PATENTS 2,296,202 9/1942 Hardy 264-1682,604,667 7/1952 Hebler 264-168 2,604,689 7/1952 Hebler 264-1682,948,583 8/1960 vAdams et al.

2,957,747 l0/l960' Bowling.

3,002,804 10/1961 Kilian 264--181 3,215,486 ll/1965 Hada et al.

3,330,897 7/1967 Tessier.

3,337,487 8/1967 Vandenberg 260-79 3,361,859 1/1968 Cenzato.

3,365,431 1/1968 Gorban et al. 260-79.7 3,382,306 5/1968 Oppenlander264-178 3,408,435 10/1968 Logan et al.

3,426,754 2/1969 Biernbaum et al. 128-156 3,432,590 3/1969 Papps 264-290X 3,347,969 10/ 1967 Moelter 264-210 JULIUS FROME, Primary Examiner I.H. WOO, Assistant Examiner U.S. Cl. X.R.

Docket No. IE UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No, Dated November lo,

Invencods) Walter J. Polestak It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as show-n below:

In Column l# line 66, replace "l-g" with "1-8g" Signed and sealed thisLith day of January 1 972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer ActingCommissioner' of Paten FORM PO-1050(1D6S) iwi ii n i

